My MacBook hard drive has 12 GB of mysterious hidden files, and nothing seems to know what they are | Mac

I recently noticed that my MacBook’s 120 GB SSD was almost full, despite having only around 78 GB of total files. I couldn’t locate any of the mysterious other stuff taking up space on the drive, so I tried updating the OS to Mojave, and that dropped me down to 90 GB usage, despite 78 GB of files. I’ve tried everything I can think of, and it’s got my computer-y friends baffled. (At this point, I’m considering reformatting the drive, but I don’t want to do that if it’s not going to fix things/part of the hard drive is actually dead).

I’ve been working on this for days. Here is a list of things that I have tried that have not freed up the mysterious 12 GB space:

-First Aid in Disk Utility

-Deleting & disabling Time Machine snapshots

-Clearing every cache and temporary file I can think of

-scanning /Volumes/

-disabling csrutil and running all of the above again

-JDisk

-Disk Inventory X

-DaisyDrive (I don’t want to pay $10 to buy the real version because I don’t think it will be able to help)

-Onyx (all repair and maintenance scripts)

-CleanMyMac

And here are some screenshots of what’s going on